Add docker files to run the website locally

Dockerfile

+FROM ruby:2.5
+RUN mkdir /app
+WORKDIR /app
+RUN gem install bundler
+COPY Gemfile /app/Gemfile
+COPY Gemfile.lock /app/Gemfile.lock
+RUN bundle install
+COPY . /app
+RUN bundle exec rake build
+EXPOSE 4000
+CMD ["bundle", "exec", "jekyll", "serve", "--host", "0.0.0.0"]
\ No newline at end of file

README.md

@@ -7,12 +7,13 @@ KDE themed and not liable to offend. If you have a general blog you may want to
 subscribe the feed for that tag only to Planet KDE.
 
 ## Adding your feed
+
 Anyone in the KDE group on invent.kde.org can add new feeds to this repository.
 
 If you want to get your feed added, we prefer Merge Requests via [invent.kde.org](https://invent.kde.org/websites/planet-kde-org).
 
-* Fork this repository
-* Edit [planet.ini](https://invent.kde.org/websites/planet-kde-org/tree/master/planet.ini) and add:
+- Fork this repository
+- Edit [planet.ini](https://invent.kde.org/websites/planet-kde-org/tree/master/planet.ini) and add:
 
 ```ini
 [id]         # replace id with your feed's unique identifier (a-z0-9-_) (eg. kde-dot)
@@ -26,8 +27,8 @@ If you want to get your feed added, we prefer Merge Requests via [invent.kde.org
              #   gsoc
 ```
 
-* Upload your avatar to [hackergotchi directory](https://invent.kde.org/websites/planet-kde-org/tree/master/hackergotchi)
-* Send a Pull Request
+- Upload your avatar to [hackergotchi directory](https://invent.kde.org/websites/planet-kde-org/tree/master/hackergotchi)
+- Send a Pull Request
 
 If you do not have a Git account, <a href="https://bugs.kde.org/enter_bug.cgi?product=planet%20kde">file
 a bug in Bugzilla</a> listing your name, Git account (if you have one), IRC nick (if you have one), RSS or
@@ -76,11 +77,25 @@ your blog.
 For further guidance on good practice see the <a href="https://www.kde.org/code-of-conduct/">KDE Code of Conduct</a>.
 
 ## Development environment
+
 To run this website locally, use the following commands:
+
 ```sh
 bundler install
 bundler exec rake build
 bundler exec jekyll serve
 ```
+
 and visit [127.0.0.1:4000](http://127.0.0.1:4000)
 
+If you don't have Ruby on your system or simply prefer a docker / docker-compose workflow:
+
+```sh
+docker-compose up --build --detach
+```
+
+and when you're done:
+
+```sh
+docker-compose down
+```

docker-compose.yml

+version: "3.4"
+services:
+  planet-kde-org:
+    build:
+      context: ./
+    ports:
+      - "4000:4000"